1. Field of the Invention
The present invention relates to encoding apparatuses and methods, decoding apparatuses and methods, image processing systems and methods, and recording media. More specifically, the present invention relates to an encoding apparatus and method, a decoding apparatus and method, an image processing system and method, and a recording medium for preventing unauthorized copying using analog signals.
2. Description of the Related Art
Recently, digital recording and playback apparatuses adapted to record content, such as television programs, onto recording media, such as hard disks (HDs) and digital versatile disks (DVDs), by means of digital signals have increasingly become popular.
With the increase in the popularity of digital recording and playback apparatuses using HDs and DVDs as recording media, subscribers or users have been able to easily record television programs onto such recording media with high quality.
The popularity of the digital recording and playback apparatuses also provide the opportunity for unauthorized copying of commercial content, such as DVD content, of television programs, movies, and so forth.
FIG. 1 shows an example structure of an image processing system 1 that plays back content recorded on a recording medium to display the content on a display and that records the played back content onto another recording medium.
In FIG. 1, the image processing system 1 includes a playback apparatus 11, a display 12, and a recording apparatus 13. The playback apparatus 11 plays back an image signal of content recorded on a recording medium, such as an optical disk, e.g., a DVD, and obtains an analog image signal Van. The display 12 displays, as an image, the analog image signal Van output from the playback apparatus 11. The recording apparatus 13 performs recording onto a recording medium, such as an optical disk, using the analog image signal Van output from the playback apparatus 11.
The playback apparatus 11 includes a decoder 21 and a digital-to-analog (D/A) converter 22. The decoder 21 decodes an encoded digital image signal read from a recording medium (not shown), and supplies the decoded digital image signal to the D/A converter 22. The D/A converter 22 converts the digital image signal supplied from the decoder 21 into an analog image signal Van, and outputs the analog image signal Van.
The display 12 is composed of, for example, a cathode-ray tube (CRT), a liquid crystal display (LCD), or the like. The display 12 displays, as an image, the analog image signal Van from the D/A converter 22, and allows the user to view the image corresponding to the image signal recorded on the recording medium.
The analog image signal Van output from the playback apparatus 11 is also supplied (input) to the recording apparatus 13.
The recording apparatus 13 includes an analog-to-digital (A/D) converter 31, an encoder 32, and a recorder 33, and records the input analog image signal Van onto a recording medium (not shown), such as an optical disk.
The analog image signal Van output from the playback apparatus 11 is supplied to the A/D converter 31. The A/D converter 31 converts the supplied analog image signal Van into a digital image signal Vdg, and supplies the digital image signal Vdg to the encoder 32. The encoder 32 encodes the digital image signal Vdg from the A/D converter 31, and supplies the encoded digital image signal, namely, Vcd, to the recorder 33. The recorder 33 records the encoded digital image signal Vcd onto a recording medium.
In the image processing system 1 having the above-described structure, the analog image signal Van output from the playback apparatus 11 is used to record an image signal onto a recording medium different from the played back recording medium. There is also a possibility of unauthorized copying of content (i.e., an image signal of content) using the analog-image signal Van output from the playback apparatus 11.
In an approach of the related art to prevent such unauthorized copying using the analog image signal Van, when copyright is protected, the analog image signal Van is scrambled and is then output, or the output of the analog image signal Van is prohibited. This approach is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2001-245270.
Another approach is to provide a digital video apparatus disclosed in Japanese Unexamined Patent Application Publication No. 10-289522. In this digital video apparatus, a compression decoder on the playback side or a compression encoder on the recording side or both the decoder and the encoder include a noise information generator, and noise information that cannot be identified at the time of image playback by one iteration of processing is embedded in digital video data so that the image can be copied although the image that is copied a plurality of times is greatly degraded in quality, thereby substantially limiting the number of times copying can be performed.
The approach disclosed in Japanese Unexamined Patent Application Publication No. 2001-245270, in which the analog image signal Van is scrambled and is then output or the output of the analog image signal Van is prohibited, can prevent unauthorized copying. However, there arises another problem of also preventing a normal image from being displayed on the display 12.
The approach disclosed in Japanese Unexamined Patent Application Publication No. 10-289522, in which noise information is embedded by the compression decoder on the playback side or the compression encoder on the recording side, needs a noise information generator and a circuit for embedding the noise information, thus increasing the circuit size.
The present inventors have proposed a technique for preventing unauthorized copying using analog image signals without problems, such as the prevention of displaying an image and the increased circuit size. This technique is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2004-289685.